Ball milling polymerization

There are other methods of preparation that iavolve estabhshing an active phase on a support phase, such as ion exchange, chemical reactions, vapor deposition, and diffusion coating (26). For example, of the two primary types of propylene polymerization catalysts containing titanium supported on a magnesium haUde, one is manufactured usiag wet-chemical methods (27) and the other is manufactured by ball milling the components (28). 

ZrCl2 prepared by disproportionation of ZrCl3 without ball-milling was also active (about 80 g C2H4/g ZrCl2 hr at 20 kg/cm2 and 75°C) in ethylene polymerization (157, 159). 

In Benning el al. (146) some data on the kinetics of ethylene polymerization in the presence of TiCl2 activated by ball-milling are given. Polymerization was studied at 140-260°C (the solution process in cyclohexane). The first orders of the polymerization rate on the monomer and catalyst concentrations have been established. The polymerization decreased with temperature a sharp drop in rates at about 180-200°C was observed. 

Finally, dye-doped microparticles of irregular form can be produced by grinding or ball milling of polymeric monoliths provided that the material is brittle enough to... 

Schematic diagrams of the apparatus, designed in our lab at< y, are shown in Fig. 1. Polymer flakes are placed, with a balls of about 5 mm dieter, in a glass an oule A about 4 cm in diameter and 7 cm in length. To the other end of the ampoule an ESR sample tube B is attached. Through connector C, the ampoule can be connected to a vacuum system and then evacuated to 10 mm Hg. After evacuation the connector is sealed off and the ampoule is removed from the vacuum system. The evacuated ampoule is now placed on a vibrator, wWch moves vertically at about 4 cycle per second. The procedure can be carried out in a Dewar flask containing coolant, such as liquid nitrogen, to fix the temperature. After some hours of this vibration, the crushed flakes are transferred to the ESR sample tube without raising the temperature of the sample. Ihen, sample tube containing the fractured flakes is placed in an ESR cavity at controlled temperature. The ball-mill apparatus permitted polymeric materials to be crushed in vacuum at low temperature and the ESR spectrum to be observed without contamination of oxygen.

According to [12], one of the reasons why binding properties appear in quartz sand and aluminosilicates is the accumulation of silicic or aluminosilicic acids and their polymerization during activation followed by stabilization (intensive stirring). The concentration of silicic acid in the suspension increases during treatment in ball mill to 0.5 g/1 in neutral medium and to 20.5 g/1 in alkaline medium. 

Figure 2. Changes in degree of polymerization and copper number of cotton cellulose during milling with a Norton ball mill. Key Y, milled fiber V, O,...

Mechanochemically Initiated Graft Copolymerization. According to the ESR study, it is clear that mechanoradicals were generated in cellulose either by means of mechanical cutting or ball milling. These mechanoradicals may be utilized as reaction sites for the initiation of vinyl polymerization which would result in graft copolymerization of cellulose. Based on this principle, the ability of cellulose mechanoradicals to initiate copol3nnerization was pursued. 

Solvents can be eliminated from some reactions by running them in ball mills.57 Methyl methacrylate can be polymerized in a vibratory ball mill using a talc catalyst.58 Ball mills are feasible for reactions on a commercial scale. Huge mills are used by the mining industry in grinding ores before flotation. If the mill is used repeatedly to make the same product, the problem of cleaning it out between runs is eliminated. It is also possible to use an inert liquid diluent in the milling, so that the product can be recovered as a slurry. The preferred diluent would be water if it is inert for the reaction in question. 

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